The present invention relates to a rotation limiting device for selectively locking a first member relative to a second member at a desired angular position. The present invention also relates to a seat recliner device using such a rotation limiting device.
A conventional seat recliner device typically uses a combination of gear teeth and a pawl for selectively retaining the seat back at a desired angular position relative to the seat bottom. Due to the nature of engagement between gear teeth and a pawl, such a recliner device is capable of angular adjustment only in a discrete manner or can be locked only at a number of discrete angular positions. This disadvantage is particularly pronounced when a recliner device is provided on each side of the seat because the two recliner devices may not be properly synchronized due to dimensional or positional errors. For instance, the two recliner devices may fail to lock simultaneously or may be locked simultaneously only if the seat back is undesirably twisted.
Providing a recliner device on each side of the seat is beneficial in ensuring the mechanical strength of the seat back against tilting. This is particularly important when the upper end of the seat belt is anchored to the seat back because the seat back is required to withstand the tension of the seat belt at the time of a vehicle crash or other high acceleration situations.
Japanese patent laid-open publication No. 10-234507 discloses a reclining limiting device for a seat back using a ball-type one-way clutch. When this ball-type one-way clutch is used in such an orientation that the locking action of the one-way clutch resists the forward reclining movement of the seat back, the high mechanical resistance of the locking action enables a highly firm retention of the angular position of the seat back against forward tilting. When this ball-type one-way clutch is used in the opposite orientation, the locking action of the one-way clutch resists the rearward reclining movement of the seat back.
However, because this previously proposed arrangement is capable of preventing the rotation in only one direction, it is required to be installed in addition to the conventional recliner device using other retaining means. This adds to the complexity of the recliner device, and increases both the size and weight of the vehicle.
In view of such problems of the prior art, a primary object of the present invention is to provide a rotation limiting device which is capable of locking at any desired position, and resisting rotation in either direction.
A second object of the present invention is to provide a rotation limiting device which can provide a high mechanical strength against rotation by using a relatively simple structure.
A third object of the present invention is to provide a rotation limiting device which is suited to be incorporated in a seat recliner device.
A fourth object of the present invention is to provide a seat recliner device incorporated with such a rotation limiting device.
A fifth object of the present invention is to provide a seat recliner arrangement which ensures a favorable synchronism between two seat recliner devices provided on either side of the seat.
According to the present invention, these and other objects of the present invention can be accomplished by providing a rotation limiting device for selectively preventing a relative rotation between two members, comprising: a first member including an inner cam member defining a substantially circular outer circumferential surface; a second member supported by the first member for relative rotation around a center of the outer circumferential surface and defining a substantially circular inner circumferential surface disposed coaxially with respect to the outer circumferential surface so as to define an annular gap between the inner and outer circumferential surfaces; a first roller member received in the annular gap so as to be selectively wedged between the inner and outer circumferential surfaces to oppose a relative rotation of the first and second members in a first direction; a second roller member received in the annular gap so as to be selectively wedged between the inner and outer circumferential surfaces to oppose a relative rotation of the first and second members in a second direction which is opposite from the first direction; and an actuation member which is adapted to act upon the roller members so as to selectively disengage the roller members from an wedging engagement between the inner and outer circumferential surfaces.
Because the engagement between the first and second members is accomplished by the wedging of roller members, which may include any members that can roll including, not exclusively, cylindrical rollers, balls, and other elliptic and hourglass shaped members, the first and second members can be held rotationally fast to each other in a continuous manner or at any desired angular position. If the roller members have a circular profile, the chamber receiving the roller members should have a relatively wide middle part and circumferential ends which get progressive narrower toward their ends, and each of the roller members should be narrower than the relatively wide middle part of the chamber, but wider than the circumferential ends of the chamber.
According to a preferred embodiment of the present invention, a spring member, typically consisting of a compression coil spring interposed between the roller members, is disposed in the annular gap to urge the roller members so as to be wedged between the inner and outer circumferential surfaces. The actuation member may consist of a first actuation member and a second actuation member which are rotatably supported by one of the first and second members, and each of the actuation members may be provided with an axial projection which is adapted to act upon a corresponding one of the roller members to displace it away from a corresponding one of the narrower circumferential ends of the chamber against a spring force of the spring member. The actuation members can be actuated by hand via a lever member, by an end of a power transmission member such as a pull cable, or by an electric motor or other power actuators.
Such a rotation limiting device is very suitable for use in a seat recliner device. For instance, a seat recliner device according to the present invention may comprise a seat bottom bracket adapted to be attached to a seat bottom and incorporated with an inner cam member defining a substantially circular outer profile; a seat back bracket adapted to be attached to a seat back and pivotally joined with the seat bottom bracket, the seat back bracket defining a recess defining a chamber in cooperation with the outer profile of the inner cam member, the chamber including a relatively wide middle part and gets progressive narrower toward each circumferential end; a pair of roller members receives in the chamber, each of the roller members being narrower than the relatively wide middle part of the chamber, but wider than the circumferential ends of the chamber; a spring member which normally urges the roller members toward the corresponding narrower circumferential ends; a release member supported by the seat bottom bracket so as to be moveable between a lock position for allowing the roller members urged by the spring member toward the narrower circumferential ends and a release position for displacing the roller members away from the narrower circumferential ends against a spring force of the spring member.
Such a seat recliner device may be used on one side of a seat so that a fine adjustment of the angular position may be achieved. It is also possible to use such a seat recliner device capable of continuous angular adjustment as a slave seat recliner device while a more conventional seat recliner device capable of only step-wise adjustment is used as a master seat recliner device. Thereby, the two seat recliner devices can be synchronized so that the two seat recliner devices can be successfully locked simultaneously at all times without involving any twisting of the seat back.